1. Field of the Invention
This invention relates to lubricating oils. More specifically, this invention relates to protective oils for equipment with copper alloy components as in polyethylene compressors.
2. Discussion of the Prior Art
Heretofore it was well known in the lubricating art to provide white mineral oil lubricants for compressors, as is disclosed in W. A. Potanina, E. N. Marcheva, E. N. Sidlyaronok, S. K. Bogdanov, T. P. Ponomareva "NKM-40 naphthenic compressor oil used in the production of polyethylene". Khim. Technol. Topliv Masel, No. 1 (1978) 22-23; and E. N. Marcheva, W. A. Potanina, G. T. Fuks, "Production of NKM-40 White Oil Compressor Lubricant From the West Siberian Crudes" Khim. Technol. Topliv Masel, No. 7 (1984) 11-12.
It was also known in the prior art to provide amounts of oleic acid in white mineral oil as friction modifier, such as disclosed in British Patent No. 1,338,505. The continued presence of oleic acid in the blends used for copper based alloy parts lubrication caused unnecessary chemical wear. That is, oleic acid provided good lubricity, but its continual presence caused unnecessary chemical wear because of its ongoing reactivity with the copper-containing alloy.
Other lubricating compositions used certain phosphates and oleates as anti-wear additives, such as disclosed in U.S. Pat. No. 3,970,570 to Pratt, et al.
Wisotsky, U.S. Pat. No. 4,505,829 discloses the use of glycerol monoleate and glyceroi dioleate as stabilizing additives for the lubricating oil. Waldmann, U.S. Pat. No. 3,235,449 also discloses the use of partial esters of glycerols for foam stabilization in lubricants.
British Patent No. 1,340,804 discloses a lubricating composition for a two-stroke internal combustion engine. That composition includes the synergistic combination of a polybutene or polyisobutylene with a triglyceride of an unsaturated aliphatic carboxylic acid containing 18 carbon atoms, with the triglyceride to polymer ratio being 1:10 to 1:30.
Culpon, U.S. Pat. No. 5,156,759 discloses the use of di and tri synthetic polyol esters as solubilizers for other additives in polyalphaolefin base oil.
In the art relating to the lubrication of equipment with copper bearing alloy surfaces, there was the specific problem of chemical wear caused by the oleic acid friction modifier. The art therefore desired an oil that not only improved frictional characteristics but exhibited a high level of protection against copper base alloy chemical wear.